Uranium Enrichment

Just Plain Facts to Fuel an Informed Debate on Nuclear Proliferation and Nuclear Power

By Arjun Makhijani, Ph.D., Lois Chalmers, and Brice Smith, Ph.D.

There is one element that occurs in nature that has been the raw material for nuclear bombs: uranium, chemical symbol U. Uranium occurs in nature as a mixture of three different isotopes – that is, three different atomic weights that have virtually the same chemical properties, but different nuclear properties (see Appendix 1: Uranium: Its Uses and Hazards). These isotopes are U-234, U-235, and U-238. The first is a highly radioactive trace component found in natural uranium, but it is not useful in any applications; the second isotope is the only fissile material2 that occurs in nature in significant quantities, and the third is the most plentiful isotope (99.284 percent of the weight of a sample of natural uranium is U-238), but it is not fissile. U-238 can, however, be split by high energy neutrons, releasing large amounts of energy and is therefore often used to enhance the explosive power of thermonuclear, or hydrogen, bombs.

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